In practice, it has been found that the progression of the heating of the raw anodes during the heating phase is of key importance for the quality of the final anodes produced by sintering. In particular, it has been found that the heating gradient reached during the heating phase is decisive for the quality of the anodes. In particular, a high heating gradient, in particular a heating gradient >14° K/h, can lead to the formation of cracks in the anode. Since, in the case of high-density anodes, a particularly high tendency for crack formation can be determined and since it has not previously been possible in practice to implement the much lower heating gradients, in particular heating gradients <8° K/h, which are necessary to avoid crack formation, when heating raw anodes of relatively high density compared to the heating of raw anodes of relatively low density, anodes of relatively high density therefore were not previously produced in “open annular kilns” in industrial practice, these kilns being operated in a vacuum environment with no covering of the kiln chamber. Instead, anodes of high density were previously fired substantially exclusively in “covered” firing kilns, which have much lower efficiency however compared to open annular kilns however.